The present invention is concerned with die apparatus which is employed to form a flange-like annular upset upon a straight length of tubing or to otherwise fixedly clamp such a length of tubing with the annular upset enclosed within the die while the length of tubing is still attached to an indeterminate length of tubing stock which is axially advanced through the die when the die is opened so that flanged tubing parts may be formed or handled by the die on a mass production basis.
Such tubing parts are employed in large numbers by the automotive industry, typically in vacuum powered systems. Conventionally, tubing from a supply coil is passed through a straightener and feeding device of well known construction to a forming die which, when closed, will fixedly clamp two axially spaced sections of the tubing between two separate die member pairs. While the tubing is so clamped, one of the die member pairs is driven axially toward the other and the resultant compression of the relatively short section between the two clamped portions of the tubing causes this section to expand radially outwardly to form an annular upset or flange on the tubing. One of the die pairs has its cavity formed with an enlarged diameter section to receive this flange. After the upset is formed, the die members are opened and the tubing is axially advanced to move the flanged section clear of the die and simultaneously bring a new tube section into the die. The flanged section may proceed directly from the die to a cutoff device, or it may be advanced to a second die which will clamp the tubing while some other work operation is performed on the flanged length of tubing.
In such an operation, the tubing is fed along a substantially fixed axial path which extends through the die. Conventionally, the separable die members are split on a horizontal plane with the lower die member held against vertical movement and the upper die member moving vertically between the die open and closed position, as by a conventional hydraulic cylinder. This arrangement enables the semi-circular cross-sectioned tube receiving recess in the lower die member to serve as a tube guide.
In order to perform the upsetting of the tube which creates the annular flange-like upset, the two sections of the tube which are gripped by the dies must be clamped very firmly in the die so that no slippage between the die and tube occur during the upsetting operation. Thus, hangup of the formed part in one of the die sections upon opening of the die is a frequent occurrence, and because one of the die members, namely the lower member, is fixedly mounted and the tube is typically engaged by feeding means both upstream and downstream of the die which are aligned with the recess in the lower die member, the tube typically will tend to remain seated in the lower die member upon opening of the die. Subsequent actuation of the feeding means to advance the flanged tubing axially through the die is hindered by the fact that the freshly formed flange is seated within the enlarged diameter portion of the die cavity provided to control the flange formation.
The present invention is especially directed to a die apparatus designed to minimize the foregoing problems.